Surface for playing fields

ABSTRACT

SPECIAL SURFACES FOR PLAYING FIELDS COMPRISING AN UPPER LAYER, A1, A MIDDLE LAYER A2 AND A LOWER LAYER A3, LAYERS A1 AND A3 CONSISTING OF A THERMOPLASTIC MOLDING MATERIAL HAVING A SPECIAL COMPOSITION. THE LAYERS A1 AND A3 ARE WEBS OR BOARDS HAVING PARALLEL RIBS ON ONE SIDE, AND THE LAYER A2 IS A STRIP OR SHEET OF STEEL OR PLASTICS MATERIAL. THE RIBS ON THE LAYERS A1 AND A3 ARE IN CONTACT WITH THE MIDDLE LAYER A2 AND ARRANGED IN SUCH A WAY THAT THEY ARE STAGGERED AT EQUAL DISTANCES IN REALTION TO EACH OTHER.

Aprii 1971 HANS-GEORG TRIESCHMANN ETAL 3,575,780

SURFACE FDR PLAYING FIELDS Filed May 6, 1969 INVENTORS HANS-GEORG TRIESCHMANN LEO UNTERSTENHOEFER SIEGFRIED MAIER HEINZ BERBNER ATT'YS United States Patent US. Cl. 161123 Claim ABSTRACT OF THE DISCLOSURE Special surfaces for playing fields comprising an upper layer a a middle layer a and a lower layer a layers a and a consisting of a thermoplastic molding material having a special composition. The layers a and a are webs or boards having parallel ribs on one side, and the layer a is a strip or sheet of steel or plastics material. The ribs on the layers a and a are in contact with the middle layer a and arranged in such a way that they are staggered at equal distances in relation to each other.

The present invention relates to surfaces in the form of webs or boards for playing fields.

Conventional surfaces of playing fields generally consist of:

(1) water-bound inorganic material, for example fine red gravel and tufaceous sand (particularly outdoors);

(2) asphalt or cement;

(3) wood (particularly indoors); and

(4) linoleum or polyvinyl chloride (particularly indoors).

It is known that these surfaces have a number of disadvantages. Water-bound inorganic surfaces (1) are for example not weather-resistant, require a great deal of attention and are only slightly resilient. Asphalt and cement surfaces (2) are for example too hard and lack the desired resilience. Wooden surfaces (3) are for example expensive, require considerable attention and are not resilient enough Linoleum and polyvinyl chloride surfaces (4) are for example practically devoid of elasticity.

More recently, attempts have been made to obviate the said disadvantages by the use of plastic surfaces. These surfaces fall substantially into two groups: (I) compressible, inherently resilient monolithic surfaces, for example those based on polyurethanes; and (II) surfaces in which compressible substances, such as relatively small particles of rubber or cork, are bonded together with a plastic binder, such as vinyl chloride, acrylate or isobutylene polymers.

As is well known, the said plastic surfaces have a number of advantages over conventional surfaces, but they leave much to be desired in some respects, e.g. increasing resiliency is accompained by a decrease in hardness and consequently an increasing loss of energy, particularly when the surface is loaded for short intermittent periods for example by runners. Another disadvantage is that any damage to the surface can only be repaired with considerable trouble.

The object of the present invention is to provide surfaces which do not have the said disadvantages or only 3,575,780 Patented Apr. 20, 1971 (a) They comprise an upper layer a a middle layer a and a lower layer a the upper layer a and the lower layer a each being a web or board 3 to 10mm. in thickness which has on one side only parallel ribs having a height of from 1 to 5 mm., a cross-sectional area of from 2 to, 25 mm. and being spaced apart at a distance of from 5 to 20 mm., and the middle layer a being a strip or sheet of steel having a thickness of from 0.1 to 0.8 mm. or a strip or sheet of plastic material having a Shore A hardness of from 40 to and a thickness of from 0.5 to 2.5 mm., this layer a being devoid or substantially devoid of any ribs, the ribs of the upper layer a and the lower layer a being in contact with the middle layer a and arranged in such a way that they are staggered at equal distances in relation to each other; and

(b) The upper layer a and lower layer a are prepared from a thermoplastic molding material which has a mean elongation of from 400 to 800% and a modulus of elasticity of from 60 to kg./cm. and which consists or substantially consists of (b 100 parts by weight of bitumen, (b from 50 to parts by weight of an ethylene polymer, and, if desired, (b up to 100 parts by weight of a filler.

The following details are given concerning the structure (a) of the surface:

As the thickness of the upper layer a increases, there is an increase in hardness and at the same time an increase in elasticity of the surface (with the same middle and lower layers a and a The elasticity of the surface (with the same upper and lower layers a, and a can also be influenced by varying the thickness, and consequently the stiffness, of the middle layer a A change in the thickness of the lower layer a;, has practically no effect on the hardness and eleasticity of the surface. The height and cross-sectional area of the ribs of the upper layer a and lower layer a affect the hardness and elasticity of the surface. As the height increases, the cross-sectional area remaining constant, there is a decrease in hardness and a decrease in elasticity. The cross section may advantageously have the shape of a circle, semicircle, square, ellipse or hemiellipse (ratio of axes in the latter two cases up to about 1:4), a rectangle (ratio of sides up to about 1:4) or a swallow-tail (ratio of small side to large side up to about 1:6). The distance between the ribs on the lower layer a affects the hardness and elasticity of the surface, i.e. as the distance increases, the hardness and resilience decrease. In this connection it should be pointed out that the shape of the upper layer a need not be the same as that of the lower layer a It may be advantageous for example for the thickness of the upper layer a to be greater than that of the lower layer a;,.

From the foregoing it can be seen that surfaces according to this invention may easily be given practically any hardness and resilience by appropriate choice of the dimensions of the three layers.

The thermoplastic molding materials (b) for the production of the upper layer a and the lower layer a to be used according to this invention are known. They are described for example in Italian patent specifications Nos. 707,289 and 779,373, in UK. patent specification No. 1,042,303 and in the published papers of Belgian Patent No. 694,900. It has been found that molding materials which are very suitable consist or substantially consist of (b 100 parts by Weight of bitumen having a penetration (according to DIN 1995) of from 10 to 210, (b 80 to 100 parts by weight of an ethylene polymer which contains from 3 to 70 parts by weight of polymerized units of n-butyl acrylate per 100 parts by weight of ethylene. In this connection it should be mentioned that the thermoplastic molding material for the upper layer al need not be the same as the molding material for the lower layer a Thus for example it may be advantageous in some cases to use a composition containing a filler for the upper layer a and a composition without filler for the lower layer (1 The production of the two layers a and :1 of the surface may be carried out by methods such as are conventionally used for the thermoplastic molding materials (b) in question. Layers a and a may advantageously be prepared for example by molding the material at atmospheric pressure (at temperatures of from about 200 to 280 C.) in appropriate horizontal molds (for the production of boards) or by extruding the molding material (at operating temperatures of from about 100 to 160 C.) through slot dies (production of webs).

The production of the surfaces from the three layers a a and (1 may also be carried out by methods such as are conventionally employed for the thermoplastic molding materials (b) used, particularly by bonding or fusion.

Suitable subgrades for the surfaces according to this invention are hard surfaces which should be as level as possible, eg the conventional surfaces given above under (1) and (2).

Application of the surface to the subgrade may be carried out by methods such as are conventionally used for plastic surfaces, for example by simply placing into position or by bonding.

Any damage to the surfaces according to this invention can be repaired on the spot by heating the surface to temperatures of from about 180 to 240 C. (so that the material becomes plastic) and smoothing it down, if necessary with the addition of heated fresh molding material.

The accompanying drawing shows a surface in accordance with this invention having an upper layer a a middle layer a and a lower a It can be seen from the drawing that the upper layer a and the lower layer a each consists of a web or board having parallel ribs on one side, the ribs on the upper layer a and on the layer a being in contact with the middle layer a and arranged in such a way that they are staggered at equal distances in relation to each other.

We claim.

1. A surface for playing fields in the form of webs or boards (a) which is composed of an upper layer a a middle layer a and a lower layer a the upper layer a and the lower layer a each being a web or board 3 to 10 mm. in thickness provided on one side only with parallel ribs having a height of from 1 to 5 mm., a cross-sectional area of from 3 to 25 mm. and being spaced apart at .a distance of from 5 to 20' mm., and the middle layer a being a strip or sheet of steel having a thickness of from 0.1 to 0.8 mm. or a strip or sheet of a plastic material having a Shore A hardness of from 40 to 90 and a thickness of from 0.5 to 2.5 mm., this layer a being devoid or substantially devoid of any ribs, the ribs of the upper layer a and the lower layer a being in contact with the middle layer and arranged in such a way that they are staggered at equal distances in relation to each other; and (b) whose upper layer a and lower layer a are prepared from a thermoplastic molding material having a mean elongation of from 400 to 800% and a modulus of elasticity of from 60 to 100 kg./cm. and consisting essentially of (b 100 parts by weight of bitumen, (b from to 100 parts by weight of an ethylene polymer and (b up to 100 parts by weight of a filler.

References Cited UNITED STATES PATENTS 2,076,122 4/1937 -Duryee 16l-123 2,194,364 3/1940 Minor l61123X 2,534,137 12/1950 Lewis 161-123 3,064,279 11/ 1962 Finkle 161-122X 3,222,697 12/ 1965 Scheermesser l61--123X 3,242,509 3/ 1966 Nissen 272X 5 ROBERT F. BURNETT, Primary Examiner S. M. HOFFMAN, Assistant Examiner US. Cl. X.R.

mg UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,575,7 0 Dated April 20, 1971 Inventofls) Hans -Georg Trieschmann et al It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 2, line E I, "eleasticity" should read elasticity Column line 8, Claim 1, "3" should read 2 line 23, "100" should read 120 Signed and sealed this 13th day of July 1971.

(SEAL) Attest:

EDWARD M.FLETGHER,JR. WILLIAM E. SGHUYLER, JR. Attssting Officer Commissioner of Patents 

